/Engine/Source/Runtime/ImageCore/Public/DDSFile.h
The latter is somewhat arbitrary. D3D9 DDS files don't store whether pixels for a texture are meant to be interpreted as sRGB or not. This reader treats the resulting formats as non-sRGB UNORM, so the writer does the same for symmetry.
[EDDSError](API\Runtime\ImageCore\UE__DDS__EDDSError) WriteDDS ( TArray64< uint8 > & OutDDS, [EDDSFormatVersion](API\Runtime\ImageCore\UE__DDS__EDDSFormatVersion) InFormatVersion )